Mmm, the only 454 I'm familiar with was a Chevy engine. A 1966 T-bird should have a 390 or, optionally as designated by a 'Q' in the appropriate part of the data plate, a 428.
During the *late* 60s the family of engines comprising the 390 and 428 was gradually superseded by the 429 and then the 460, a newer design of big block. It is not unheard of for those to be retrofitted to an early or mid 60s T-bird with a blown engine (sometimes accompanied with a C-6 transmission, which *was* correct for some '66 Birds as the Cruise-O- Matic was phased out), but they weren't original.
You can find out more about your car by taking down all the numbers off the data plate on the driver's door and looking at the decoder on
http://www.tbird.org